Turned the forest entrance slime into a bat at night.
Dropped context support on the editor.
Upgraded the tileset loading format to deharcode tileset names in map data files.
Remove some code spaghetti in the editor and ironed it out a bit against invalid data.
Adapted the game code to the latest tileset format.

Now, the tileset image is read in the tileset definition file.
Removed a supoerfluous parameter in the tilesets definition files.

The file_name parameter was pointing to the self file name,
which can't useful, except with lazy code.
Adapted the map files to the latest map format available.